Protozoa

Protozoa

[pro″to-zo´ah]

a subkingdom (formerly a phylum) comprising the unicellular eukaryotic organisms; most are free-living, but some lead commensalistic, mutualistic, or parasitic existences. According to newer classifications, the Protozoa are divided into seven phyla: Sarcomastigophora, Labyrinthomorpha, Apicoplexa, Microspora, Acetospora, Myxozoa, and Aliophora. Pathogenic protozoa include Plasmodium species, the cause of human malaria; Trypanosoma gambiense, the cause of African trypanosomiasis; Toxoplasma gondii, of which house cats are the reservoir and humans the intermediate host; Entamoeba histolytica, the cause of amebic dysentery; and Balantidium coli and Isospora belli, both of which cause diarrhea in humans.

Protozoa can be ingested and transmitted through contaminated feces. Prevention of transmission is extremely important; handwashing and stool precautions are recommended. Other necessary precautions (see infection control) should be carried out according to directions from the Centers for Disease Control and Prevention. Protozoal infections are occurring more frequently in North America and other industrialized countries because of increased world travel.

protozoa

Pro·to·zo·a

(prō'tō-zō'ă),

Formerly considered a phylum, now regarded as a subkingdom of the animal kingdom, including all of the so-called acellular or unicellular forms. They consist of a single functional cell unit or aggregation of nondifferentiated cells, loosely held together and not forming tissues, as distinguishes the Animalia or Metazoa, which include all other animals. Protozoa were formerly divided into four classes: Sarcodina, Mastigophora, Sporozoa, and Ciliata; new classifications employ higher taxa (phyla, subphyla, and superclasses) and a number of major subdivisions.

[proto- + G. zōon, animal]

Protozoa

/Pro·to·zoa/ (-zo´ah) a subkingdom comprising the simplest organisms of the animal kingdom, consisting of unicellular organisms ranging in size from submicroscopic to macroscopic. It comprises the Sarcomastigophora, Labyrinthomorpha, Apicomplexa, Microspora, Acetospora, Myxozoa, and Ciliophora.

protozoon

[prō′təzō′ən]pl. protozoa

Etymology: Gk, protos + zoon, animal

a unicellular protist that ingests food. Protozoa include free-living forms, such as amebas and paramecia, as well as parasites. Approximately 30 protozoa are pathogenic to humans, including Plasmodium, which causes malaria, and Trypanosoma, which causes sleeping sickness. See also mastigophora. protozoal, protozoan,adj.

Pro·to·zo·a

(prō'tō-zō'ă)

Formerly considered a phylum, now regarded as a subkingdomof the animal kingdom, including all of the so-called acellular or unicellular forms. Members consist of a single functional cell unit or aggregation of nondifferentiated cells, loosely held together and not forming tissues.

[proto- + G. zōon, animal]

Protozoa

(prōt″ă-zō′ă) [ proto- + -zoa]

PROTOZOA

PROTOZOA

PROTOZOA

PROTOZOA

PROTOZOA

PROTOZOA

The phylum of the kingdom Protista that includes unicellular, animal-like microorganisms. Many protozoa are saprophytes that live on dead matter in water and soil. Many parasitic protozoa infect only humans without adequate immunological defenses although a few infect the immunocompetent. Infections are spread by the fecal-oral route, through ingestion of food or water contaminated with cysts or spores, or by the bite of a mosquito or other insect that has previously bitten an infected person. Common protozoan infections include malaria (Plasmodium vivax, P. malariae); gastroenteritis (Entamoeba histolytica, Giardia lamblia); leishmaniasis, an inflammatory skin or visceral disease (Leishmania species); sleeping sickness (Trypanosoma brucei gambiense, T. b. rhodiense); and vaginal infections (Trichomonas vaginalis). Pneumocystis jiroveci, previously classified as a protozoon, is now categorized as a fungus. Opportunistic protozoan infections caused by Cryptosporidium parvum and Toxoplasma gondii are seen in patients who are immunosuppressed by disease or drug therapy. See: illustration; table

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